Nowadays, a variety of digital cinema projection apparatuses use a digital light processing (DLP) technology to perform digital projection. For meeting the brightness request to project image onto a large-size screen and complying with the color request which was developed by Digital Cinema Initiative (DCI), the lighting system for the conventional digital cinema projection apparatus is usually equipped with a xenon lamp as a light source. Since the optical spectrum of the xenon lamp in the visible light range is close to the sunlight spectrum, the xenon lamp may readily achieve the color request for DCI. In addition, the xenon lamp can output power in a very wide range. For example, since the power range of the xenon lamp is from 1200 W to 7000 W, the xenon lamp is sufficient to project digital cinema onto a large-size screen. However, the xenon lamp still has some drawbacks. For example, the xenon lamp has bulky volume, low power conversion efficiency and high cost. Because of these drawbacks, it is difficult to reduce the volume and cost of conventional digital cinema projection apparatus.
Generally, the small-sized optical projection apparatus does not need to comply with the color request of DCI. Since it is not necessary for the small-sized optical projection apparatus to project the wide-range image onto the large-size screen, the small-sized optical projection apparatus is usually equipped with an ultra high pressure (UHP) mercury lamp as a light source. Since the UHP mercury lamp has many benefits such as low cost, small volume and long life, the use of the UHP mercury lamp is helpful for reducing the overall cost of the whole optical projection apparatus. However, since the optical spectrum of the UHP mercury lamp is not close to the sunlight spectrum, the use of the UHP mercury lamp in the digital cinema projection apparatus fails to comply with the color request of DCI.
Therefore, there is a need of providing a lighting system for a digital cinema projection apparatus by using an ultra high pressure mercury lamp as a light source in order to comply with the color request of DCI and reduce the overall volume and cost.